Autodesk 235B1-05A761-1301 User Guide - Page 682

Because primitives do not represent complete parts, they do not have a defined part type, size parameters, or autolayout data. A primitive is defined by a DWG file that specifies its limited configuration, and a preview image (BMP file) that facilitates its selection when users are adding primitives to parts. Because primitives are not parts, you cannot add them to catalogs. They are stored in a content folder instead. AutoCAD MEP includes primitives for many of the shapes commonly found in parts as well as for the connections that are typically required. Because the primitives include many of the modeling features that you need to build a custom parametric part, you can use them to quickly build a part model and add connections. For more information, see Modeling with Primitives on page 702. Trim Lengths and Placement Points After you finalize the model of your part, you need to define insertion behavior to ensure that your part can be placed correctly in a drawing. Insertion behavior includes specifying the placement point, or insertion point, that is used when placing the part in a drawing, and specifying the trim lengths for parts, such as fittings, that require other components to be trimmed when placing the part in a run. The Auto Layout option in the Content Builder Options dialog controls whether trim lengths and placement points can be defined for a part. When you enable this option, an Autolayout Data folder is available in the part browser that includes commands for adding trim lengths and placement points. NOTE For parametric MvParts, the Autolayout Data folder is included in the part browser by default, enabling you to define the placement point directly during the modeling process. Trim Lengths Trim lengths are available only when creating a parametric fitting. Configured to work with the Auto Layout option enabled, trim lengths define the length dimensions used to trim other components to make room for a new fitting. For example, when you add a tee to an existing run in your drawing, the segment is trimmed to the length of the trunk, creating 2 individual segments, 1 on either side of the fitting. Each trim length is defined from the center, or intersection point, of the fitting to an end, or connection point, of the fitting. To ensure components are trimmed correctly when placing a parametric part into a drawing, you must define trim lengths for the part in a specific order-left to right, then bottom to top. The number of trim lengths required for a part depends on the type of fitting and the number of connection points, as shown next: Elbows require 2 trim lengths Reducers require 2 trim lengths Tees require 3 trim lengths 664 | Chapter 14 Customizing Catalog-Based Content